The ridge horn antenna is a type of broadband antenna that is often used in communications systems. A ridge horn antenna generally includes ridges which carry electromagnetic energy from the signal source to the illumination area of the ridge horn antenna. An impedance transformer may be inserted between the ridges to match the input impedance of the antenna to the source. The antenna gain of the ridge horn antenna is typically higher than that of spiral and sinuous types of planar antennas, but generally less than most directional narrow beam antennas.
A reflector is often used to achieve a required level of gain for a highly directional antenna. A reflector antenna generally includes a reflector dish and a feed horn in one of many configurations. Two well known configurations of a feed horn antenna are the rectangular horn and cylindrical horn. In such configurations, the feed horn is a radiator mounted at the focal point of a reflector. Electromagnetic energy radiates from the feed horn to the metallic surface of the reflector dish from which it is reflected in a desired direction.
More specifically, a quad-ridge horn is an example of a ridge horn antenna and has a hollow conductive conduit usually having a circular cross section for propagation of microwaves between two points. The horn conduit may be formed of an electrically conductive material or of a non-conductive material that is plated or coated with an electrically conductive material. Moreover, to receive signals, horn antennas are dimensioned and flared to receive a concentration of low energy but discernable fields at one or more specific frequencies in the throat area of the horn.
A quad-ridge horn is dual-polarized and includes four ridges or tapered blades which aid in the propagation of the microwaves. Detectors are inserted or placed at the throat of the horn to receive the energy from the fields at the frequency or frequencies for which the horn has been designed. The horn is typically coupled to circuitry through orthogonal coaxial probes for input/output of Radio Frequency (RF) signals. Thus, external cables and connectors are necessary for transition to a planar distribution network.
Making an array of horns can be difficult because of the size requirements due to the RF input/output cabling, e.g. in higher frequency applications. Furthermore, soldering and micro-assembly during manufacture of the horn is difficult to automate resulting in higher costs and variable RF characteristics.
Additionally, some conventional dual-ridge horns with single polarization use microstrip feed lines or launches for transitions to circuitry. For example, U.S. Pat. No. 4,973,925 to Nusair et al., entitled "Double-Ridge Waveguide to Microstrip Coupling" discloses the use of modified ridges of a section of a double-ridge waveguide to match a microstrip circuit. Also, U.S. Pat. No. 4,157,550 to Reid et al., entitled "Microwave Detecting Device With Microstrip Feed Line" discloses the use of a slot in a waveguide to accommodate a microstrip feed line. However, in both patents, the microstrip circuit is positioned in the plane of the waveguide axis and the approaches are limited to single polarized dual-ridge waveguides/horns.
Additionally, U.S. Pat. No. 5,359,339 to Agrawal et al., entitled "Broadband Short-horn Antenna" discloses a horn array having a short-circuiting wall carrying a plurality of feed probes for the horns. Although the short-circuiting wall is mounted at the rear of the horn array, feed probes are used which may make it difficult to automate soldering and micro-assembly during manufacture of the horn array, resulting in higher costs and variable RF characteristics.